The production of synthesis gas, or syn gas (carbon monoxide and hydrogen) via the reaction of low molecular weight hydrocarbons, primarily methane, within a fluidized bed of catalyst in the presence of steam (steam reforming process) or oxygen (partial oxidation process) is well known. Processes wherein the light hydrocarbons are converted to syn gas within a fluidized bed of catalyst, e.g., nickel on an alpha alumina support, at elevated temperatures in the presence of both steam and oxygen (air) are also well known, and this type of process may offer particular advantages in that the molar ratio of hydrogen and carbon monoxide can be better controlled to produce a gas particularly suitable for conducting Fischer-Tropsch reactions. In conducting Fischer-Tropsch operations, it is required that the molar ratio of the hydrogen:carbon monoxide used be maintained at about 2:1.
Fluidized bed processes offer particular advantages in that they provide superior heat and mass transfer characteristics as contrasted with fixed bed processes. Fluidized processes permit substantially isothermal reactor conditions in conducting both exothermic and endothermic reactions. However, there are certain problems inherent in fluidized bed operations, notable among which is the sensitivity of the process to changes in the catalyst produced during the operation. Agglomeration and sintering of the solid catalytic particles during high temperature reactions and/or the introduction of contaminating substances into the catalyst by the feed reduces the activity of the catalyst.
During the reaction the catalytic metal component, i.e., nickel, grows in crystallite size. The alumina particles also agglomerate to adversely affect the fluidization characteristics of the bed, and the activity of the catalyst declines. Contaminants, introduced into the fluidized bed, eliminate or shield catalyst sites with further reduction of catalytic activity. Relatively high methane in the syn gas product and the decline in catalyst activity during normal operations seriously debits the process, and sooner or later the deactivated catalyst must be regenerated or replaced by fresh catalyst.